Propylene co-products from ethylene steam crackers and from fluidized catalytic cracking (FCC) have been the traditional sources of propylene for the past decades. With a high rate of growth in polypropylene uses, demand for propylene is exceeding the supply available from these traditional sources.
Reverse Flow Reactor (RFR) technology has been the subject of much development over the last 10 years, but mostly as applied to higher temperature reactions such as methane pyrolysis and steam reforming.
U.S. Pat. No. 4,704,497 to Gottlieb et al. discloses a process for dehydrogenating saturated or unsaturated hydrocarbons wherein the flow direction of the oxygen-containing gas, employed for removing coke deposits on the catalyst surface, is opposite to that for the hydrocarbon feed undergoing dehydrogenation.
U.S. Pat. No. 5,510,557 to Gartside et al. discloses catalytic dehydrogenation wherein feed is passed in one direction through the bed in a first cycle and heating gas is passed in an opposite direction in a second cycle to provide the endothermic heat of reaction and regenerate catalyst. The operation is controlled to properly balance heat absorbed during dehydrogenation and heat input during regeneration; e.g., by having catalyst of different activities over the length of the bed.
U.S. Pat. No. 7,815,873 to Sankaranarayanan et al. discloses the overall efficiency of a regenerative bed reverse flow reactor system is increased where the location of the exothermic reaction used for regeneration is suitably controlled. The disclosure provides a method and apparatus for controlling the combustion to improve the thermal efficiency of bed regeneration in a cyclic reaction/regeneration processes. The process for thermal regeneration of a regenerative reactor bed entails (a) supplying the first reactant through a first channel means in a first regenerative bed and supplying at least a second reactant through a second channel means in the first regenerative bed, (b) combining said first and second reactants by a gas mixing means situated at an exit of the first regenerative bed and reacting the combined gas to produce a heated reaction product, (c) passing the heated reaction product through a second regenerative bed thereby transferring heat from the reaction product to the second regenerative bed.
U.S. Pat. No. 7,846,401 to Hershkowitz et al. discloses increasing the overall efficiency of a regenerative bed reverse flow reactor system where the location of the exothermic reaction used for regeneration is suitably controlled. The disclosure provides a method and apparatus for controlling the combustion to improve the thermal efficiency of bed regeneration in a cyclic reaction/regeneration processes. The process for thermal regeneration of a regenerative reactor bed entails (a) supplying the first reactant through a first channel means in a first regenerative bed and supplying at least a second reactant through a second channel means in the first regenerative bed, (b) combining said first and second reactants by a gas mixing means situated at an exit of the first regenerative bed and reacting the combined gas to produce a heated reaction product, (c) passing the heated reaction product through a second regenerative bed thereby transferring heat from the reaction product to the second regenerative bed.
U.S. Published Patent Application No. 2008/0300438 to Keusenkothen et al. discloses a process for pyrolyzing a hydrocarbon feedstock containing nonvolatiles in a regenerative pyrolysis reactor system. The process comprises: (a) heating the nonvolatile-containing hydrocarbon feedstock upstream of a regenerative pyrolysis reactor system to a temperature sufficient to form a vapor phase that is essentially free of nonvolatiles and a liquid phase containing the nonvolatiles: (b) separating said vapor phase from said liquid phase; (c) feeding the separated vapor phase and methane to the pyrolysis reactor system; and (d) converting the methane and separated vapor phase in said pyrolysis reactor system to form a pyrolysis product. In another aspect, the disclosure includes a separation process that feeds multiple pyrolysis reactors.
World Patent No. 2002/051965 A1 to Van de Beld discloses a method of carrying out a cracking reaction in a packed-bed reverse flow reactor. For the purpose of maintaining the temperature of the reverse flow reactor, a less than stoichiometric amount of oxygen is added to a combustible gas comprising a compound to be cracked. According to the disclosure, there is a mixing chamber between two packed beds into which oxygen is supplied. The disclosure also describes a preferred embodiment, in which a mixing chamber is provided between three beds, which in time periodically fulfill a different role.
“A Novel Reverse Flow Reactor Coupling Endothermic And Exothermic Reactions”, parts I and II to M. van Sint Annaland et al., Chemical Engineering Science, 57, (2002), pp. 833-854 (part I) and pp. 855-872 (part II), discloses a reactor concept for highly endothermic heterogenously catalysed gas phase reactions at high temperatures with rapid but reversible catalyst deactivation, by indirect coupling of energy necessary for endothermic reactions, such as propane dehydrogenation, and energy released by exothermic reactions, without mixing of the endothermic and exothermic reactants, in a closed-loop reverse flow operation. Two different reactor configurations are considered: a sequential reactor configuration, where the endothermic and exothermic reactants are fed sequentially to the same catalyst bed acting as an energy repository, and a simultaneous reactor configuration, wherein the endothermic and exothermic reactants are fed continuously to two different compartments directly exchanging energy.
“A Novel Reverse Flow Reactor Coupling Endothermic And Exothermic Reactions: An Experimental Study”, to M. van Sint Annaland et al., Chemical Engineering Science, 57, (2002), pp. 4967-4985, discloses an experimental study of propane dehydrogenation coupled with methane combustion over a monolithic catalyst, in which back-conversion of propylene to propane is minimized by adding inactive sections flanking the catalyst at both ends.
The potential application of these reactors to lower-temperature chemistry has been speculated upon, but the details have not been developed. Accordingly, advances in RFR technology and processes are needed to enhance the effectiveness of the technology.